The authors declare no conflict of interest.
Stabilization of the prostate-specific tumor suppressor NKX3.1 by the oncogenic protein kinase Pim-1 in prostate cancer cells†
Article first published online: 14 MAR 2013
Copyright © 2012 Wiley Periodicals, Inc.
Journal of Cellular Biochemistry
Volume 114, Issue 5, pages 1050–1057, May 2013
How to Cite
Padmanabhan, A., Gosc, E. B. and Bieberich, C. J. (2013), Stabilization of the prostate-specific tumor suppressor NKX3.1 by the oncogenic protein kinase Pim-1 in prostate cancer cells. J. Cell. Biochem., 114: 1050–1057. doi: 10.1002/jcb.24444
- Issue published online: 14 MAR 2013
- Article first published online: 14 MAR 2013
- Accepted manuscript online: 5 NOV 2012 12:13PM EST
- Manuscript Accepted: 24 OCT 2012
- Manuscript Received: 24 AUG 2012
- PROSTATE CANCER;
- Pim-1 KINASE;
Loss of NKX3.1 is an early and consistent event in prostate cancer and is associated with increased proliferation of prostate epithelial cells and poor prognosis. NKX3.1 stability is regulated post-translationally through phosphorylation at multiple sites by several protein kinases. Here, we report the paradoxical stabilization of the prostate-specific tumor suppressor NKX3.1 by the oncogenic protein kinase Pim-1 in prostate cancer cells. Pharmacologic Pim-1 inhibition using the small molecule inhibitor CX-6258 decreased steady state levels and half-life of NKX3.1 protein but mRNA was not affected. This effect was reversed by inhibition of the 26S-proteasome, demonstrating that Pim-1 protects NKX3.1 from proteasome-mediated degradation. Mass spectrometric analyses revealed Thr89, Ser185, Ser186, Ser195, and Ser196 as Pim-1 phospho-acceptor sites on NKX3.1. Through mutational analysis, we determined that NKX3.1 phosphorylation at Ser185, Ser186, and within the N-terminal PEST domain is essential for Pim-1-mediated stabilization. Further, we also identified Lys182 as a critical residue for NKX3.1 stabilization by Pim-1. Pim-1-mediated NKX3.1 stabilization may be important in maintaining normal cellular homeostasis in normal prostate epithelial cells, and may maintain basal NKX3.1 protein levels in prostate cancer cells. J. Cell. Biochem. 114: 1050–1057, 2013. © 2012 Wiley Periodicals, Inc.